sql server 2016 – How to renew certificates in an availability group without downtime?

OK, here is the setup. We have two nodes, both running SQL Server 2016, participating in an availability group. Both servers are running on Windows Server 2016 and are NOT joined to an Active Directory domain.

Each server has a certificate, and the other node uses that certificate to connect to it and authenticate.

The certificates need to be replaced since their expiration date is approaching.

It seems like you have to update the certificate on server A, or create a new one, then copy it to server B, then change server B to use that for authentication. However it seems like during the middle of this process, there will be downtime since the “old” certificate will no longer be accepted by server A. This whole process would then need to be repeated again for server B’s certificate – creating even more downtime. This seems like a bad situation!

The question is – how to do this without causing server or cluster downtime?

Any help would be greatly appreciated. Also if you have any tips on how to generate the certificates with a 3 year expiration instead of 1 year that will be great. These servers are running on a private network so I think the risk of private key leak is very low.